High performance tire characterized by “fuel-efficiency, high security and high durability” has become a major development direction in tire industry. Incorporation of silica into a tread rubber may significantly enhance wet-traction and reduce rolling resistance of the tire. Silica has become an essential filler in high performance tread rubber. In order to further improve the performance of the tread rubber containing silica, a silylation treatment, especially for sulfur-containing silane, is often used in the manufacture of tire tread rubber. Through such treatment, interfacial property between silica and rubber can be significantly improved. However, an amount of the sulfur-containing silane widely used in the industry is quite high (for example, 10 wt % relative to silica). It is well-known that silylation reactions between the silane and the filler are very complicated, including not only condensation reactions between alkoxy groups and surface hydroxyl groups (such as silanol groups) of the filler, but also hydrolysis reactions and condensation reactions among the alkoxy groups, which results in a very low silylation efficiency. Not only an excessive amount of the silane increases manufacturing costs, but side reactions related to the silane affect the performance of the rubber, and controllability of an interfacial structure becomes poor as well. So far, there's no effective method for reducing the amount of silane or enhancing use efficiency of the silane in the manufacture of the tread rubber. Therefore, exploring a methodology that effectively catalyzes the silylation reaction in the tread rubber is expected to greatly enhance the use efficiency of silane and the controllability of the structure, and hence to improve the interfacial performance of rubber composite materials and dispersion of the filler. Thus dynamic performance of the tread rubber is effectively improved. This method possesses important theoretical significance and practical significance for the manufacture of the high-performance tire.
Ionic liquids refer to ionic molten salts having a melting point below 100° C. and they have been greatly used in many fields such as green solvents, catalysis and electrochemistry. Depending on different central atoms and substituent groups, cations of the ionic liquid substantially belongs to an onium salt. Owing to an interaction between polar groups of the ionic liquid and surface hydroxyl groups of silica (such as hydrogen-bond interaction), the cations of the ionic liquid can be adsorbed to the surface of silica. Onium ions of the ionic liquid which are adsorbed to the surface of silica can activate the silanol groups through a charge effect, i.e. generating silanolate anions Generation of the silanolate anions is a prerequisite step for the condensation between siloxane and silanol group. Therefore, the silylation reaction between the siloxane and the filler can be significantly catalyzed by the ionic liquids.